1. Field of the Invention
This invention relates to magnetic material for use in direct current magnetic applications, and more particularly, it pertains to uncoated microlaminations of annealed low carbon steel.
2. Description of the Prior Art
Pressed and sintered iron powders are currently used in many direct current applications, such as pole faces for DC motors, and for use in a myriad of applications as shown in U.S. Pat. No. 3,235,675. Compacts of this type often replace punched and assembled hot rolled laminated steel (pole steel), ingot iron, or electromagnetic iron. The advantage of the sintered powdered iron over the punched lamination steel and the machined ingot or electromagnetic iron is that the process is scrapless, whereas all alternate methods generate scrap. The disadvantage of pressed and sintered powdered iron compacts is that the magnetic quality is generally inferior to the other materials used in DC applications.
Microlaminations are small rectangular particles that have been cut from low carbon steel or other soft magnetic alloy sheet. Thereafter, the particles are annealed, coated with an electrically insulating material and compressed into a magnetizable compact. Such compacts exhibit magnetic properties, specifically an acceptable core loss, that permits their use in a variety of alternating current magnetic applications. Prior art patents disclosing microlaminations used as magnetizable compacts include U.S. Pat. Nos. 3,848,331 and 3,948,690.
Although a loss level is a requirement for a material used in alternating current apparatus, the low core loss level is not a major need for material used in direct current devices. The most important direct current requirement is a high permeability, low coercive force, and high saturation induction level. The permeability and coercive force of the microlamination compacts when processed as previously described, are considerably poorer than the sintered powdered iron, the ingot iron, the pole steel, and the electromagnetic iron.